Strombus(2006) - ISSN 0104-7531 Accounts on the phylogeny of the Rissooidea (=Hydrobioidea) and Littorinoidea, based on some American representatives, as base for a future taxonomic revaluation (Mollusca, Caenogastropoda). Luiz Ricardo L. Simone¹ ¹ Museu de Zoologia da Universidade de São Paulo; Cx. Postal 42494; 04299-970 São Paulo, SP, Brazil. email: [email protected] Abstract This paper is developed based on descriptive studies published elsewhere. It aims to analyze the morphological data on a set of littorinoidans and rissooideans looking for the understanding their phylogeny and their relationships with remaining Caenogastropoda taxa. The examined set of species is relatively small, but considered sufficient for above mentioned analysis. The phylogenetic study revealed the monophyly of the Rissooidea, being the littorinoideans a paraphyletic arrangement of basal branches. A total of 44 morphological characters (59 states) is analyzed. Its analysis resulted in the following cladogram: (Littorina flava (Annularia sp (Amphithalamus glabrus (Potamolithus ribeirensis (P. karsticus – P. troglobius))))). A set of 14 morphological synapomorphies supports this monophyly. Key words: Littorinoidea, Rissooidea, Caenogastropoda, Morphology, Phylogeny. Resumo Este estudo é desenvolvido baseado em estudos descritivos publicados em outros artigos. O objetivo é analisar os dados de um conjunto de Littorinoidea e Rissooidea, na procura do entendimento de sua filogenia e seu relacionamento com os restantes Caenogastropoda. O conjunto de espécies analisadas é relativamente pequeno, mas considerado suficiente para a supracitada análise. O estudo filogenético revelou a monofilia de Rissooidea, sendo Littorinoidea um arranjo parafilético de ramos basais. Um totalde 44 caracteres morfológicos (59 estados) é analisado. Sua análise resultou no seguinte cladograma (Littorina flava (Annularia sp (Amphithalamus glabrus (Potamolithus ribeirensis (P. karsticus – P. troglobius))))). Um conjunto de 14 sinapomorfias morfológicas suporta esta monofilia. Palavras-chave: Littorinoidea, Rissooidea, Caenogastropoda, Morfologia, Filogenia. Introduction A phylogenetic approach, regarded as preliminary, had been published by Ponder (1988), The superfamily Rissooidea, also called giving base for an on going larger project encompassing Rissoidea, Hydrobioidea and Truncatelloidea, more representatives. This project is still being encompasses at least 27 families (Vaught, 1989). Most performed, based mainly on molecular data (Ponder, of them assemble minute sized species, with personal communication). The author has obtained the representatives having some millimeters in length. They monophyly of the Rissooidea, but did not consider the are one of the more diverse and adaptable animals, littorinoideans. occurring in practically all environments suitable for a As part of a larger project on phylogenetic mollusk. There are representatives in thermal founts, relationship of the order Caenogastropoda, at the in phreatic pools, in caves, in marine, freshwater and superfamily level, three features of each superfamily terrestrial habitats, etc. has been examined: 1) their monophyly; 2) the fact in The superfamily Littorinoidea encompasses being really an independent taxon, i.e., separated from about 5 families (Vaught, 1989), presenting close the others; and 3) the ground plan. The three features relationship with the Rissooidea, with same widespread are only reached by means of phylogenetic analysis. range of environment. No sure separation between Representing the Superfamilies Rissooidea and Rissooidea and Littorinoidea had been pointed up to Littorinoidea, species were selected for detailed date, except that the littorinoideans generally present morphological study and to base a comparative and species with larger size, having about 1 – 2 cm. cladistic analysis. The morphological study on each Strombus (13)2:18-26, jul-dez. 2006 18 Accounts on the phylogeny of the Rissooidea ... species has been published elsewhere. The present As outgroups, the other Caenogastropoda up to study is a preliminary approach, necessary in the main now studied in the project were selected. They are project. Although the paper of Ponder (1988) is very mainly the following: Cerithioidea (Simone, 2001); important, and has been used in the present project, it Architaenioglossa (Simone, 2004b); Stromboidea has not aims to some important data for this (e.g., the (Simone, 2005); Cypraeoidea (Simone, 2004a); odontophore muscles) and also does not analyze the Calyptraeoidea (Simone, 2002); Tonnoidea (Simone, littorinoideans. These facts imply in additional studies. 1995c); Muricoidea (Simone, 1995d on Thala crassa; However, in a so diverse and rich taxon, a full analysis Simone, 1996a on Buccinanops spp); Conoidea would demand more time and effort than the analysis (Simone, 1999, 2000 on Terebridae). As more distant of the remaining caenogastropods together. Thus, it outgroups, some archaeogastropods were also was idealized to analyze, at the moment, a small analyzed (e.g., Simone, 1996b; 1997; Leal & Simone, sample, very away from the ideal number of species 1998, 2000). In the discussion, some specific outgroup for representing the group, but at least sufficient for a taxa are mentioned, based upon own observed or on preliminary study on the relationship between the literature data. On the other hand, in the matrix of rissooideans and littorinoideans, and these with characters (Table 1) only the ground plan of the remainder caenogastropods. This study will serve as Cerithioidea (Simone, 2001). The ground plan of this base and scenario for future studies. superfamily is chosen in the sense of being more The main objective of the present paper is to representative, however, the final result is the same if perform a phylogenetic analysis of a sample of the ground plan was substituted by anyone of the 19 rissooideans and littorinoideans, attempting for (terminal) species present in that paper. Each character, analyzing them in the study on the Caenogastropoda state, and polarization is justified in the following section as a whole. in such, if necessary, a concise explanation or discussion is presented. Material and Methods The discussion of each character is also based on the analysis of the obtained tree (Fig. 1). Although The morphological study, including the list of the matrix of characters (Table 1) and the subsequent examined species, was, or has been submitted to be, cladrogram (Fig. 1) are shown only in section following. published. Although the several species anatomically The synapomorphies of the ingroup, (superfamily known in the literature have been consulted, the present autapomorphies) are preserved in present paper, just analysis only considers the following species: 1) because they are the main concern as referred in the Amphithalamus glabrus Simone, 1995a (Barleeidae), introduction. The ingroup autapomorphies are the base from São Paulo coast, Brazil. 2) Littorina flava (King & for a better establishment a still imprecise taxon. They Broderip, 1832) (Simone, 1998) (Littorinidae), from confirm the internal position of some possible coast of Venezuela and Brazil. 3) Annularia sp (Simone, “outgroups” such as littorioideans. They will be useful 2004b) (Annulariidae), terrestrial species from Mexico; in the on going phylogenetic study of the entire order 4) Potamolithus ribeirensis (Pilsbry, 1911). 5) P. Caenogastropoda as the ground plan of the superfamily. troglobius (Simone & Moracchioli, 1994). 6) P. karsticus Additionally, they are in agreement with some (Simone & Moracchioli, 1994), these 3 species phylogenetic approach of studies on other groups (e.g., belonging to the freshwater family Hydrobiidae, Yeates, 1992; Pinna, 1996). collected in rivers and caves of south São Paulo (see Some multistate characters are here analyzed Simone & Moracchioli, 1994). under an additive (ordered) approach. In each case, The following section of comparative morphology the additive concept is justified in the discussion and is organized as a phylogenetic analysis, the account is always based on the ontogeny or on the fact in being on each character begins with abbreviated descriptive each state a clear modification of the preceding one. sentence followed by plesiomorphic and derived Moreover, each additive multistate character was also conditions(s); also included CI and RI (consistency and analyzed as non-addictive, and any fortuitous change retention indices, respectively), values for the character in the result and/or indices are also reported. under the most parsimonious hypothesis. Following The cladistic analysis was performed with the the apomorphic state(s), a list of terminal taxa with the aid of the computer program “Tree Gardner 2.2” (Ramos, apomorphic condition is presented. Hundreds of 1997), which basically works as an interface of the characters were selected, based on the examined Hennig86 (Farris, 1988). The used algorithm was “ie”. sample. Those that resulted autapomorphic, highly The computer program PAUP was also used. Both variable, or overlapping, were selected but not included programs presented the same result. in the cladistic analysis. The remainder characters were organized in states, coded, polarized comparing with outgroups, and a cladistic analysis was performed. 19 Strombus (13)2, 2006 L.R.L. Simone Discussion of characters 2. Head-foot 1. Shell 6. Ommatophore: 0= absent; 1= present (Littorina flava, Annularia sp) (CI= 50; RI= 50). 1. Size: 0= about 30 mm; 1: about